Display device

ABSTRACT

According to an embodiment of the present invention, a display device includes a backlight unit that is divided into a plurality of blocks and is driven by the divided blocks, and includes at least one optical assembly, a display panel positioned over the backlight unit, a controller that outputs local dimming values corresponding to brightness of the blocks of the backlight unit, in accordance with an image displayed in the display panel, and a BLU driver that controls brightness of the blocks of the backlight unit using the local dimming values.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of co-pending U.S. patent applicationSer. No. 12/796,130 filed on Jun. 8, 2010 which claims priority under 35U.S.C. §119(e) on U.S. Provisional Application No. 61/237,587 filed onAug. 27, 2009 35 U.S.C. §119(a) and on Patent Application No.10-2009-0113711 filed in Republic of Korea on Nov. 24, 2009, the entirecontents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display device, in more detail, amethod of driving a backlight unit included in a display device.

2. Description of the Related Art

Demands for display devices have been increased in various ways with thedevelopment of information society, and a variety of display deviceshave been correspondingly studied and used in recent years, includingLCDs (Liquid Crystal Display Device), PDPs (Plasma Display Panel), ELD(Electro Luminescent Display), VFD (Vacuum Fluorescent Display).

Among others, the liquid crystal panel of the LCDs includes a liquidcrystal layer, and a TFT substrate and a color filter substrate facingeach other with the liquid crystal layer therebetween and cannot emitlight by itself, such that it can display images with the use of lightprovided from a backlight unit.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method ofefficiently driving a backlight unit of a display device, and a displaydevice using the method.

A display device according to an embodiment of the present inventionincludes: a backlight unit that is divided into a plurality of blocks,driven for each of the divided blocks, and includes at least one opticalassembly; a display panel that is disposed above the backlight unit; acontroller that outputs local dimming values for each blockcorresponding to the brightness of the blocks in the backlight unit, inaccordance with an image displayed on the display panel; and a BLUdriver that controls the brightness of the blocks in the backlight unit,using the local dimming values for each block; in which the opticalassembly includes: a first layer; a plurality of light sources formed onthe first layer and emitting light; a second layer disposed above thefirst layer to cover the light sources; and a reflective layer that isdisposed between the first and second layers, and the BLU driver outputsa plurality of driving signals in response to the input local dimmingvalues for each block, and the driving signals each control thebrightness of two or more blocks in the blocks of the backlight units.

A display device according to another embodiment of the presentinvention includes: a backlight unit that is divided into a plurality ofblocks, driven for each of the divided blocks, and includes at least oneoptical assembly; a display panel that is disposed above the backlightunit; a controller that outputs local dimming values for each blockcorresponding to the brightness of the blocks in the backlight unit, inaccordance with an image displayed on the display panel; and a BLUdriver that controls the brightness of the blocks in the backlight unit,using the local dimming values for each block, in which the opticalassembly includes: a first layer; a plurality of light sources formed onthe first layer and emitting light; a second layer disposed above thefirst layer to cover the light sources; and a reflective layer that isdisposed between the first and second layers, the BLU driver includes andriving unit, and the driving unit includes a controller that receiveslocal dimming value for each block from the controller and a pluralityof driver ICs outputting driving signals for controlling the brightnessof the two or more blocks.

A display device according to another embodiment of the presentinvention includes: a backlight unit that is divided into a plurality ofblocks and is driven by the divided blocks, and includes at least oneoptical assembly; a display panel positioned over the backlight unit; acontroller that outputs local dimming values corresponding to brightnessof the blocks of the backlight unit, in accordance with an imagedisplayed in the display panel; and a BLU driver that controlsbrightness of the blocks of the backlight unit using the local dimmingvalues, wherein the optical assembly includes: a first layer; aplurality of light sources that are formed on the first layer and emitlight, and a light emitting surface of the light source being formed inthe direction crossing the first layer, and at least two of the lightsources emitting lights in different directions from each other; asecond layer disposed above the first layer to cover the light sources;and a reflective layer that is disposed between the first and secondlayers, wherein the BLU driver receives the local dimming values andoutputs a plurality of driving signals, and the driving signals controlthe brightness of two or more blocks among the blocks of the backlightunit respectively.

A display device according to another embodiment of the presentinvention includes: a backlight unit that is divided into a plurality ofblocks and is driven by the divided blocks, and includes at least oneoptical assembly; a display panel positioned over the backlight unit; afirst controller that outputs local dimming values corresponding tobrightness of the blocks of the backlight unit, in accordance with animage displayed in the display panel; and a BLU driver that controlsbrightness of the blocks of the backlight unit using the local dimmingvalues, wherein the optical assembly includes: a first layer; aplurality of light sources that is are formed on the first layer andemit light, and a light emitting surface of the light source beingformed in the direction crossing the first layer, and at least two ofthe light sources emitting lights in different directions from eachother; a second layer disposed above the first layer to cover the lightsources; and a reflective layer that is disposed between the first andsecond layers, and wherein the BLU driver includes a driving unit, andthe driving unit includes a second controller that receives localdimming values from the first controller and a plurality of driver ICsthat output driving signals for controlling the brightness of the two ormore blocks respectively.

According to a backlight unit of an embodiment of the present invention,it is possible to reduce the thickness of a display device, simplify themanufacturing process of the display device and improve the externalappearance by disposing the backlight unit in close contact to a displaypanel. Further, it is possible to improve the contrast of a displayedimage, using a partial driving method, such as local dimming.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view showing a configuration of adisplay device.

FIG. 2 is a cross-sectional view schematically showing a configurationof a display module.

FIG. 3 is a cross-sectional view showing a configuration of a backlightunit according to a first embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a configuration of a backlightunit according to a second embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a configuration of a backlightunit according to a third embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a configuration of a backlightunit according to a fourth embodiment of the present invention.

FIG. 7 is a cross-sectional view showing a configuration of a backlightunit according to a fifth embodiment of the present invention.

FIG. 8 is a plan view showing an embodiment of an arrangement structureof a plurality of light sources in a backlight unit according to thepresent invention.

FIG. 9 is a plan view showing an embodiment of a positional relationshipbetween the light sources arrange in the backlight unit.

FIG. 10 is a plan view showing an embodiment of the shape of alight-shielding pattern formed in the backlight unit.

FIG. 11 is a cross-sectional view showing a configuration of a backlightunit according to a sixth embodiment of the present invention.

FIG. 12 is a cross-sectional view showing a configuration of a displaydevice according to an embodiment of the present invention.

FIG. 13 is a block diagram schematically showing the configuration ofthe display device according to a first embodiment of the presentinvention.

FIG. 14 is a block diagram schematically showing the configuration ofthe display device according to a second embodiment of the presentinvention.

FIG. 15 is a graph showing a first embodiment of a method of determiningbrightness of a light source according to a average luminance level ofan image.

FIG. 16 is a graph showing a second embodiment of a method ofdetermining brightness of a light source according to the averageluminance level of an image.

FIG. 17 is a graph showing an embodiment of a method of determining acompensating value of an image signal to the average luminance level ofan image.

FIG. 18 is a block diagram schematically showing a configuration of aBLU driver.

FIG. 19 is a block diagram showing an embodiment of the configuration ofthe BLU driver.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is described hereafter with reference to theaccompanying drawings. The embodiment described hereafter can bemodified in various ways and the technical spirit of the embodiments isnot limited to the following description. The embodiments are providedfor those skilled in the art to fully understand the present invention.Therefore, the shape and size of the components shown in the drawingsmay be exaggerated for more clear explanation.

FIG. 1 is an exploded perspective view showing the configuration of adisplay device.

Referring to FIG. 1, a display device 1 includes a display module 20, afront cover 30 and a back cover 40 which cover the display module 20,and fixing members 50 that fixes the display module to the front cover30 and/or the back cover 40.

Meanwhile, the front cover 30 may include a front panel (not shown) madeof a transparent material transmitting light and the front panel isdisposed at a predetermined distance from the display module 20, indetail, at the front of a display panel (not shown) included in thedisplay module to protect the display module 20 from an external shockand transmit light emitted from the display module 20 such that an imagedisplayed on the display module 20 can be seen from the outside.

The fixing members 50 have one side fixed to the front cover 30 byfasteners, such as screws, and the other side supporting the displaymodule 20 with respect to the front cover 30 such that the displaymodule 20 can be fixed to the front cover 30.

Although the fixing member 50 exemplified by a long plate in thisembodiment, it may be possible to implement a configuration in which thedisplay module 20 is fixed to the front cover 30 or the back cover 40 byfasteners, without the fixing members 50.

FIG. 2 is a cross-sectional view schematically showing the configurationof a display device according to an embodiment of the present invention,in which a display module 20 of the display device may include a displaypanel 100 and a backlight unit 200.

Referring to FIG. 2, the display panel 100 includes a color filtersubstrate 110 and a TFT (Thin Film Transistor) substrate 120 facing andbonded to each other with a uniform gap, and a liquid crystal layer (notshown) may be disposed between the substrates 110 and 120.

The color filter substrate 110 includes a plurality of pixels composedof red R, green G, and blue B sub-pixels and can create an imagecorresponding to the red, green, or blue color when light is applied.

Meanwhile, although the pixels may be composed of the red, green, andblue sub-pixels, this configuration is not necessarily limited theretoand may be implemented in various combinations, such as when one pixelis composed of red, green, blue, and white W sub-pixels.

The TFT substrate 120 is a switching element that can switch pixelelectrodes (not shown). For example, a common electrode (not shown) andthe pixel electrode can change the arrangement of molecule in thecrystal layer in response to a predetermined voltage applied from theoutside.

The liquid crystal layer includes a plurality of liquid crystalmolecules and the liquid crystal molecules change the arrangement inresponse to the voltage difference generated between the pixel electrodeand the common electrode. Accordingly, the light emitted from thebacklight unit 200 can travel into the color filter substrate 110 bychanges in the arrangement of the liquid crystal molecules.

Further, an upper polarizer 130 and a lower polarizer 140 may bedisposed on and beneath, respectively, the display panel, and in detail,the upper polarizer 130 may be disposed on the color filter substrate110 and the lower polarizer 140 may be disposed beneath the TFTsubstrate 120.

On the other hand, a gate generating driving signals for driving thepanel 100 and a data driving unit (not shown) may be provided at thesides of the display panel 100.

The structure and configuration, described above, of the display panel100 are just exemplified and the embodiment may be modified, added, andremoved within the spirit of the present invention.

As shown in FIG. 2, the display device according to an embodiment of thepresent invention may be configured by disposing the backlight unit 200in close contact to the display panel 100.

For example, the backlight unit 200 may be bonded and fixed to the lowersurface of the display panel, in detail, to the lower polarizer 140, andfor this configuration, an adhesive layer (not shown) may be providedbetween the lower polarizer 140 and the backlight unit 200.

By disposing the backlight unit 200 in close contact to the displaypanel 100, as described above, it is possible to reduce the entirethickness of the display device to improve the external appearance andit is also possible to simplify the structure of the display device andthe manufacturing process by removing a structure for fixing thebacklight unit 200.

Further, since the space between the backlight unit 200 and the displaypanel 100 is removed, it is possible to prevent the display device fromthe display device and the image quality of display images fromdeteriorating due to foreign substances inserted in the space.

According to an embodiment of the present invention, the backlight unit200 may be formed by stacking a plurality of function layers and atleast one of the function layers may be provided with a plurality oflight sources (not shown).

Further, it is preferable that the backlight unit 200, in detail, thelayers of the backlight unit 200 are made of a flexible material inorder to fix the backlight unit 200 in close contact to the lowersurface of the display panel 100, as described above.

Further, a bottom cover (not shown) where the backlight unit 200 isseated may be provided under the backlight unit 200.

According to an embodiment of the present invention, the display panel100 may be divided into a plurality of regions and the brightness of thelight emitted from corresponding regions of the backlight unit 200, thatis, the brightness of corresponding light sources is adjusted inresponse to the gray peak values or color coordinate signals of thedivided regions, such that the luminance of the display panel 100 can beadjusted.

For this configuration, the backlight unit 200 may operate in aplurality of driving regions divided to correspond to the dividedregions of the display panel 100.

FIG. 3 is a cross-sectional view showing the configuration of abacklight unit according to a first embodiment of the present invention,in which the backlight unit 200 may include a first layer 210, lightsources 220, a second layer 230, and a reflective layer 240.

Referring to FIG. 3, the light sources 220 may be formed on the firstlayer 210 and the second layer 230 may be disposed above the first layer210 to cover the light sources 220.

The first layer 210 may be a substrate on which the light sources 220are mounted and may be provided with an adapter (not shown) supplyingpower and an electrode pattern (not shown) for connecting the lightsources 220. For example, a carbon natotube electrode pattern (notshown) may be formed on the substrate to connect the light sources 220with the adapter (not shown).

On the other hand, the first layer 210 may be a PCB (Printed CircuitBoard) that is made of polyethylene terephthalate, glass, polycarbonate,and silicon etc. to mount the light sources 220 in a film shape.

The light source 220 can emit light at a predetermined directional anglefrom a predetermined direction and the predetermined direction may be adirection in which the light emitting surface of the light source 220 isaligned.

According to an embodiment of the present invention, the light source220 may be formed of an LED (Light Emitting Diode) and may include aplurality of LEDs. For example, the light source 220 formed of a lightemitting diode can emit light at about 120° directional angle from thedirection in which the light emitting surface is aligned.

To be specific, the LED package of the light source 220 can beclassified into a top view type and a side view type in accordance withthe direction in which the light emitting surface is aligned, and thelight sources 220 according to an embodiment of the present inventioncan be formed of at least one of a top view type LED package with thelight emitting surface upward and a side view type LED package with thelight emitting surface at a side.

The light source 220 according to an embodiment of the present inventioncan be formed of the side view type LED package.

In this case, the light emitting surface of the light source 220 can beformed in the direction crossing the first layer 210.

According to an embodiment of the present invention, the light emittingsurface of the light source 220 and the first layer 210 may cross at aright angle.

Further, the light source 220 may be formed of a color LED emitting atleast one of colors including red, blue, and green, or a white LED.Furthermore, the color LED may include at least one of a red LED, a blueLED, and a green LED, and it is possible to change the arrangement ofthe light emitting diodes and light emitted from the diodes within thescope of the embodiment.

On the other hand, the second layer 230 disposed above the first layer210 to cover the light sources 220 transmits and diffuses light emittedfrom the light sources 220 such that the light emitted from the lightsources 220 uniformly travels to the display panel 100.

The reflective layer 240 reflecting the light emitted from the lightsources 220 may be disposed between the first layer 210 and the secondlayer 230, in detail, on the first layer 210. The reflective layer 240reflects again the light total-reflecting from the interface of thesecond layer 230 such that the light emitted from the light sources 220can be diffused wider.

The reflective layer 240 may be a synthetic resin sheet with whitepigments, such as titanium dioxide, diffused therein, with a metal filmdeposited on the surface, or with bubbles therein to disperse light, andsilver (Ag) may be coated on the surface to increase reflectivity.Further, the reflective layer 240 may be coated on the first layer 210,a substrate.

The second layer 230 may be made of a light-transmissive material, forexample, a silicon-based or acryl-based resin. The second layer 230,however, is not limited to the materials described above, and may bemade of various resins.

Further, the second layer may be made of a resin having about 1.4 to 1.6refractive index in order for the backlight unit 200 has uniformluminance while diffusing the light emitted from the light sources 220.

For example, the second layer 230 may be made of any one materialselected from a group of polyethylene terephthalate, polycarbonate,polypropylene, polyethylene, polystyrene, polyepoxy, silicon, and acryl.

The second layer may include a polymer resin having predeterminedadhesive property to be firmly fixed to the light sources 220 and thereflective layer 240. For example, the second layer 230 may includeacryl-based, urethane-based, epoxy-based, and melamine-based unsaturatedpolyester, methyl methacrylate, ethyl methacrylate, isobutylmethacrylate, n-butyl methacrylate, n-butyl methyl methacrylate, acrylacid, methacrylic acid, hydroxyethyl methacrylate, hydroxyl propylmethacrylate, hydroxylethyl acrylate, acrylamide, methylolacrylamide,glycidolmethacrylate, ethylacrylate, isobutyl acrylate, n-butylacrylate, 2-ethylhexyl acrylate polymer, copolymer, or terpolymer.

The second layer 230 may be formed by applying and hardeningliquid-state or gel-state resin above the first surface 210 with thelight sources 220 and the reflective layer 240 thereon, or may beseparately formed and then bonded onto the first layer 210.

Meanwhile, the larger the thickness (a) of the second layer 230, thewider the light emitted from the light sources 200 is diffused, suchthat light can be supplied to the display panel 100 at uniform luminancefrom the backlight unit 200. On the contrary, the larger the thickness(a) of the second layer 230, the more the amount of light absorbed inthe second layer 230 increases, such that the entire luminance of thelight supplied from the backlight unit 200 to the display panel 100 maybe reduced.

Therefore, it is preferable that the thickness (a) of the second layer230 is about 0.1 to 4.5 mm to supply light having uniform luminancewithout largely reducing the luminance of the light supplied from thebacklight unit 200 to the display panel 100.

The configuration of the backlight unit 200 according to an embodimentof the present invention is described hereafter in detail by way of anexample that the first layer 210 of the backlight unit 200 is asubstrate with the plurality of light sources 220 and the second layer220 is a resin layer made of a predetermined resin.

FIG. 4 is a cross-sectional view showing the configuration of abacklight unit according to a second embodiment of the present inventionand, in the configuration of the backlight unit 200 shown in FIG. 4, thesame parts as those described in connection with FIGS. 2 and 3 are notdescribed below.

Referring to FIG. 4, a plurality of light sources 220 may be mounted ona substrate 210 and a resin layer 230 may be disposed above thesubstrate 210. Further, a reflective layer 240 may be formed between thesubstrate 210 and the resin layer 230, in detail, on the substrate 210.

Further, as shown in FIG. 4, the resin layer 230 may include a pluralityof dispersed particles 231 and the dispersed particles 231 can disperseor refract incident light such that the light emitted from the lightsources 220 is diffused wider.

The dispersed particles 231 may be made of a material having refractiveindex different from the material of the resin layer 230, in detail, amaterial having refractive index higher than a silicon-based oracryl-based resin of the resin layer 230, in order to disperse orrefract the light emitted from the light sources 220.

For example, the dispersed particles 231 may be made of polymethylmethacrylate/styrene copolymer (MS), polymethyl methacrylate (PMMA),polystyrene (PS), silicon, titanium dioxide (TiO2), silicon dioxide(SiO2) etc., or may be made of combination of those compounds.

Alternatively, the dispersed particles 231 may be made of a materialhaving refractive index smaller than the material of the resin layer230, for example, may be made by creating bubbles in the resin layer230.

However, the material for the dispersed particles 231 is not limited tothe materials described above and a variety of polymers or inorganicparticles may be used.

According to an embodiment of the present invention, the resin layer 230may be made by mixing the dispersed particles 231 with liquid-state orgel-state resin, and then applying and hardening the mixture on thefirst layer 210 with the light sources 220 and the reflective layer 240thereon.

Referring to FIG. 4, an optical sheet 250 may be disposed on the resinlayer 230, and for example, the optical sheet 250 may include a prismsheet 251 and a diffusing sheet 252.

In this case, the sheets are bonded in close contact with each otherwithout a gap in the optical sheet 250, such that it is possible tominimize the thickness of the optical sheet 250 or the backlight unit200.

On the other hand, the lower surface of the optical sheet 250 may be inclose contact to the resin layer 230 and the upper surface may be inclose contact to the lower surface of the display panel 100, in detail,to the lower polarizer 140.

The diffusing sheet 252 diffuses the incident light to prevent the lighttraveling out of the resin layer 230 from partially collecting, therebykeeping the luminance of the light uniform. Further, the prism sheet 251can collect the light traveling out of the diffusing sheet 252 such thatthe light can travel perpendicularly into the display panel 100.

According to another embodiment of the present invention, in the opticalsheet 250 described above, for example, at least one of the prism sheet251 and the diffusing sheet 252 may be removed, or various functionlayers may be further included, other than the prism sheet 251 and thediffusing sheet 252.

FIG. 5 is a cross-sectional view showing the configuration of abacklight unit according to a third embodiment of the present inventionand, in the configuration of the backlight unit 200 shown in FIG. 5, thesame parts as those described in connection with FIGS. 2 and 4 are notdescribed below.

Referring to FIG. 5, a plurality of light sources 220 in the backlightunit 200 are arranged with the light emitting surfaces aligned at thesides, such that they can emit light to the sides, that is, in thedirection in which a substrate 210 or a reflective layer 240 extends.

For example, the light sources 220 may be formed by a side view type LEDpackage, and accordingly, it is possible to reduce the problem that thelight sources 220 appear like hot spots on the image and make thedisplay device as well as the backlight unit 200 slim by decreasing thethickness (a) of a resin layer 230.

FIG. 6 is a cross-sectional view showing the configuration of abacklight unit according to a fourth embodiment of the presentinvention, in which a plurality of resin layers 230 and 235 may beincluded in the backlight unit 200.

Referring to FIG. 6, the light emitted from the side of a light source220 can travel to the region where an adjacent light source 225 isdisposed, through the first resin layer 230.

A portion of the light traveling through the first resin layer 230 canbe emitted upward to the display panel 100, and for this configuration,the first resin layer 230, as described with reference to FIG. 4, mayinclude the plurality of dispersed particles 231 to disperse or refractthe light upward.

Further, a portion of the light emitted from the light source 220 cantravel into the reflective layer 240, and as described above, the lightthat have traveled in the reflective layer 240 can be reflected anddiffused upward.

Meanwhile, light having large luminance can be observed in the image,because a large amount of light can be emitted from the region aroundthe light source 220 by strong diffusion around the light source or thelight emitted substantially upward from the light source 220.

Therefore, as shown in FIG. 6, first light-shielding patterns 260 areformed on the first resin layer 230 to reduce the luminance of the lightemitted from the region around the light source 220, such that light canbe emitted at uniform luminance from the backlight unit 200.

For example, the first light-shielding pattern 260 can be formed on thefirst resin layer 230 to correspond to the position of the plurality oflight sources 220, such that it can reduce the luminance of the lightemitted upward by blocking a portion of the light emitted from the lightsource 220 and transmitting the rest.

In detail, the first light-shielding pattern 260 may be made of titaniumdioxide (TiO₂), in which it can reflect downward a portion of theincident light from the light source 220 and transmitting the rest.

According to an embodiment of the present invention, a second resinlayer 235 may be disposed on the first resin layer 230. The second resinlayer 235 may be made of a material the same as or different from thefirst resin layer 230 and can improve the uniformity in luminance of thelight from the backlight unit by diffusing light emitted upward throughthe first resin layer 230.

The second resin layer 235 may be made of a material having the samerefractive index as the material of the first resin layer 230, or may bemade of a material having different refractive index.

For example, when the second resin layer 235 is made of a materialhaving larger refractive index than the first resin layer 230, the lightemitted through the first resin layer 230 can be diffused wider.

On the contrary, when the second resin layer 235 is made of a materialsmaller than the first resin layer 230, it is possible to improvereflectivity of the light emitted through the first resin layer 230 andthen reflecting from the lower surface of the second resin layer 235,such that the light emitted from the light source 220 can easily travelalong the first resin layer 230.

Meanwhile, the first resin layer 230 and the second resin layer 235 mayeach include a plurality of dispersed particles, in which the density ofthe dispersed particles included in the second resin layer 235 may belarger than that of the dispersed particles included in the first resinlayer 230.

When the dispersed particles are included at higher density in thesecond resin layer 235, as described above, it is possible to diffusewider the light emitted upward through the first resin layer 230, andaccordingly, the light emitted from the backlight unit 200 can be madeuniform in luminance.

On the other hand, as shown in FIG. 6, second light-shielding patterns265 may be formed on the second resin layer 235 to make the lightemitted through the second resin layer 235 uniform in luminance.

For example, when large luminance is observed in the image by the lightemitted upward through the second resin layer 235 and collecting to aspecific portion, it is possible to form the second light-shieldingpattern 265 at the region corresponding to the specific portion on theupper surface of the second resin layer 235, and accordingly, it ispossible to make the light emitted from the backlight unit 200 uniformin luminance by reducing the luminance of the light at the specificportion.

The second light-shielding pattern 265 may be made of titanium dioxide(TiO₂), in which a portion of the light emitted through the second resinlayer 235 may be reflected downward from the second light-shieldingpattern 265 and the rest may transmitting it.

FIG. 7 is a cross-sectional view showing the configuration of abacklight unit according to a fifth embodiment of the present inventionand, in the configuration of the backlight unit 200 shown in FIG. 7, thesame parts as those described in connection with FIGS. 2 to 6 are notdescribed below.

A plurality of patterns 241 may be formed on a reflective layer 240 sothat the light emitted from a light source 220 can easily travel to anadjacent light source 225.

Referring to FIG. 7, the plurality of patterns 241 protruding upward maybe formed on the reflective layer 240, such that the light emitted fromthe light source 220 and then travels into the patterns 241 can bedispersed and reflected in the traveling direction.

Meanwhile, as shown in FIG. 7, the further from the light source 220,that is, the closer to the adjacent light source 225, the larger thedensity of the patterns 241 on the reflective layer 240.

For example, the further from the light source 220 emitting light towardthe reflective layer 240, the larger the density of the patterns 241.

Accordingly, it is possible to prevent the luminance of the lightemitted upward from a region far from the light source 220, that is, aregion close to the adjacent light source 225, from being reduced, suchthat the luminance of the light supplied from the backlight unit 200 canbe kept uniform.

Further, the patterns 241 may be made of the same material as thereflective layer 240, in which the patterns 241 can be formed bymachining the upper surface of the reflective layer 240.

Alternatively, the patterns 241 may be made of a different material fromthe reflective layer 240, and for example, the patterns 241 may beformed on the reflective layer 240 by dispersing or coating particles onthe reflective layer 240.

Further, the patterns 241 may be formed in various shapes, including aprism, without being limited to that shown in FIG. 7.

In addition, the patterns 241 may be depressed on the reflective layer240 and may be formed only at predetermined portions on the reflectivelayer 240.

FIG. 8 is a plan view showing the front shape of a backlight unitaccording to an embodiment of the present invention, which exemplifiesan arrangement structure of a plurality of light sources in thebacklight unit 200.

Referring to FIG. 8, the backlight unit 200 may include two or morelight sources which emit light in different directions.

For example, the backlight unit 200 may include first light sources 220and second light sources 221 which emit light from the side in parallelwith the x-axis, in which the first light sources 220 and the secondlight sources 221 may be arranged across the x-axis direction in whichlight is emitted, that is, arranged adjacent to each other in the y-axisdirection.

In other words, as shown in FIG. 8, the second light sources 221 may bearranged adjacent to the first light sources 220 in the diagonaldirection.

Meanwhile, the first light sources 220 and the second light sources 221can emit light in opposite directions, that is, the first light sources220 can emit light opposite to the x-axis direction and the second lightsources 221 can emit light in the x-axis direction.

In this configuration, the light sources in the backlight unit 200 canemit light to the sides and a side view type LED package can be used toimplement the configuration.

On the other hand, as shown in FIG. 8, the light sources of thebacklight unit 200 may be arranged in two or more rows and the two ormore light sources in the same row can emit light in the same direction.

For example, the light sources at the left and right sides of the firstlight source 220 can emit light in the same direction as the first lightsource 220, that is, opposite to the x-axis direction, and the lightsources at the left and right sides of the second light source 221 canemit light in the same direction as the second light source 221, thatis, in the x-axis direction.

It is possible to prevent the luminance of the light from concentratingor reducing in a predetermined region of the backlight unit 200 byarranging the light sources adjacent in the y-axis direction, forexample, by aligning the light-emitting direction of the first lightsources 220 and the second light sources 221 in the opposite directions.

That is, the light emitted from the first light source 220 can beweakened while traveling to an adjacent light source, and accordingly,the further from the first light source 220, the more the luminance ofthe light emitted from the corresponding region to the display panel maybe weakened.

Therefore, it is possible to compensate the concentration of luminanceof the light in the region adjacent to the light source with theweakening of luminance of the light in the region far from the lightsource by arranging the first light source 220 and the second lightsource 221 such that the light-emitting direction are opposite, as shownin FIG. 8, and it is correspondingly possible to make the luminance ofthe light emitted from the backlight unit 200 uniform.

Referring to FIG. 9, the first light sources 220 and the second sources221 may be disposed at a predetermined distance d1 from each other alongthe y-axis perpendicular to the x-axis along which light is emitted.

As the distance d1 between the first light source 220 and the secondlight source 221, there may be a region where the light emitted from thefirst light source 220 or the second light source cannot reach, suchthat the luminance of the light may be largely decreased in the region.

Meanwhile, as the distance between the first light source 220 and thesecond light source 221 decreases, there may be interference betweenlight emitted from the first light source 220 and the second lightsource 221, in which division driving efficiency of the light sourcesmay be reduced.

Therefore, the distance d1 between two adjacent light sources in thedirection crossing the light-emitting direction, that is, between thefirst light source 220 and the second light source 221 may be 9 to 27mm, in order to implement uniform luminance of the light emitted fromthe backlight unit 200 while reducing the interference between the lightsources.

Further, a third light source 222 may be disposed adjacent to the firstlight source 220 in the x-axis direction, at a predetermined distance d2from the first light source 220.

Meanwhile, the light-directional angle θ from the light source and thelight-directional angle θ′ in the resin layer 230 may have the followingEquation 1 in accordance with Snell's law.

$\begin{matrix}{\frac{n\; 1}{n\; 2} = \frac{\sin \; \theta^{\prime}}{\sin \; \theta}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

On the other hand, considering that the portion where light is emittedfrom the light source is an air layer (1 of refractive index) and thelight-directional angle θ from the light source is generally 60°, thelight-directional angle in the resin layer 230 may have the valueexpressed by the following Equation 2, in accordance with Equation 1.

$\begin{matrix}{{\sin \; \theta^{\prime}} = \frac{\sin \; 60^{{^\circ}}}{n\; 2}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

Further, when the resin layer 230 is made of acryl-based resin, such asPMMA (polymethyl methacrylate), it has refractive index of about 1.5,such that the light-directional angle θ′ of about 35.5° in the resinlayer 230 in accordance with Equation 2.

As described with reference to Equations 1 and 2, the directional angleof the light emitted from the light source in the resin layer 230 may beless than 45°, and accordingly, the range of the light emitted from thelight source and traveling in the y-axis direction may be smaller thanthe x-axis direction.

Therefore, the distance d1 between two light sources adjacent to eachother across the light-emitting direction, that is, between the firstlight source 220 and the second light source 221 may be smaller than thedistance d2 between two light sources adjacent to each other in thelight-emitting direction, that is, between the first light source 220and the third light source 222, such that the luminance of the lightemitted from the backlight unit 200 can be uniform.

Meanwhile, considering the distance d1 between the first light source220 and the second light source 221 having the above range, the distanced2 between two light sources adjacent to each other in thelight-emitting direction, that is, between the first light source 220and the third light source 222 may be 5 to 22 m, in order to reduceinterference between the light sources and make the luminance of thelight emitted from the backlight unit 200 uniform.

Referring to FIG. 9, the second light source 221 may be disposed tocorrespond to a predetermined position between the first light source220 and the third light source 222 adjacent to each other in thelight-emitting direction, that is, the x-axis direction.

In other words, the second light source 221 may be disposed adjacent tothe first light source 220 and the third light source 222 in the y-axisdirection, on the line (l) passing through between the first lightsource 220 and the third light source 222.

In this case, the distance d3 between the line (l) on which the secondlight source 221 is disposed and the first light source 220 may belarger than the distance d4 between the line (l) and the third lightsource 222.

The light emitted from the second light source 221 travels toward thethird light source 222, such that the luminance of the light emittedtoward the display panel 100 may weaken in a region around the thirdlight source 222.

Therefore, it is possible to compensate the weakening of the luminanceof light in a region around the third light source 222 with theluminance of the light concentrating in a region around the second lightsource 221, by disposing the second light source 221 closer to the thirdlight source 222 than the first light source 220, as described above.

FIG. 10 is a plan view showing an embodiment of the shape of alight-shielding pattern formed in a backlight unit, in the configurationof the backlight unit 200 shown in FIG. 10, the same parts as thosedescribed in connection with FIGS. 2 to 9 are not described below.

Referring to FIG. 10, a plurality of light-shielding patterns 260 may beformed to correspond to the positions of a plurality of light sources220.

For example, as shown in FIG. 6, light-shielding patterns 260 are formedon the first resin layer 230 covering the lights sources to reduce theluminance of the light emitted from the region around the light source220, as described above, such that light can be emitted at uniformluminance from the backlight unit 200.

According to an embodiment of the present invention, as shown in FIG.10, circular or elliptical light-shielding patterns 260 may be made oftitanium dioxide TiO2 on the resin layer 230 to correspond to thepositions of the light sources 220, such that it is possible to block aportion of the light emitted upward from the light sources 220.

FIG. 11 is a cross-sectional view showing the configuration of abacklight unit according to a sixth embodiment of the present invention.

Referring to FIG. 11, first layer 210, a plurality of light sources 220formed on the first layer, a second layer 230 covering the light sources220, and a reflective layer 240, as described with reference to FIG. 10,may be formed in one optical assembly 10, and a backlight unit 200 maybe composed of a plurality of the optical assemblies 10.

Meanwhile, N and M optical assemblies 10 of the backlight unit 200 maybe disposed in a matrix in the x-axis and y-axis directions,respectively, where N and M are integers of 1 or more.

As shown in FIG. 11, twenty one optical assemblies 10 may be arranged ina 7×3 matrix in the backlight unit 200.

The configuration shown in FIG. 11, however, is an example forexplaining the backlight unit according to the present invention and thepresent invention is not limited thereto and may be modified inaccordance with the image size etc. of the display device.

For example, for a 47 inch display device, the backlight unit 200 can beimplemented by arranging two hundred forty optical assemblies in a 24×10matrix.

Each of the optical assemblies may be an individual assembly and amodule type backlight unit may be formed by disposing them close to eachother. The module type backlight unit is a backlight member and cansupply light to the display panel 100.

As described above, the backlight unit 200 can be driven in an entiredriving type and a partial driving type, such as local dimming andimpulsive types. The driving type of the backlight unit 200 may bemodified in various ways in accordance with the circuit design and isnot modified thereto. As a result, according to the embodiment, it ispossible to the contrast and make clear the dark portion and brightportion in the image, thereby improving the image quality.

That is, the backlight unit is driven in a plurality of divided drivingregions and it is possible to brightness and definition by reducing theluminance at the dark portion and increasing the luminance at the brightportion in the image, with the luminance of the division driving regionlinked with the luminance of an image signal.

For example, it is possible to emit light upward by individually drivingonly some of the optical assemblies 10 shown in FIG. 11, and for thisconfiguration, the lights sources 220 included in the optical assemblies10 can be individually controlled.

On the other hand, the region corresponding to one optical assembly 10in the display panel 10 may be divided into two or more blocks, and thedisplay panel 100 and the backlight unit 200 may be driven in thedivided block unit.

It is possible to simplify the manufacturing process of the backlightunit 200, minimize losses that may be generated in the manufacturingprocess, and improve productivity, by combining the optical assemblies10 to form the backlight unit 200. Further, it is possible tomanufacture backlight units having various sizes by standardizing theoptical assembly of the backlight unit 200 for mass production.

Meanwhile, since when any one of the optical assemblies 10 of thebacklight unit 200 fails, it has only to replace the failed opticalassembly without replacing the entire backlight unit, the replacement iseasy and the cost needed to replace the part is reduced.

FIG. 12 is a cross-sectional view showing the configuration of a displaydevice according to an embodiment of the present invention, in theconfiguration of the display device shown in the figure, the same partsas those described with reference to FIGS. 1 to 11 are not describedbelow.

Referring to FIG. 12, a display panel 100 including a color filtersubstrate 110, a TFT substrate 120, an upper polarizer 130, and a lowerpolarizer 140 and a backlight unit 200 including a substrate 210, aplurality of light sources 220, and a resin layer 230 may be disposed inclose contact with each other.

For example, an adhesive layer 150 is provided between the backlightunit 200 and the display panel 100, such that the backlight unit 200 canbe bonded and fixed to the lower surface of the display panel 100.

In more detail, the upper surface of the backlight unit 200 can bebonded to the lower surface of the lower polarizer 140 by the adhesivelayer 150.

The backlight unit 200 may further include a diffusing sheet (not shown)and the diffusing sheet (not shown) may be disposed in close contact tothe upper surface of the resin layer 230. In this configuration, theadhesive layer 150 may be provided between the diffusing sheet (notshown) of the backlight unit 200 and the lower polarizer 140 of thedisplay panel 100.

Further, a bottom cover 270 may be disposed under the backlight unit200, and for example, as shown in FIG. 12, the bottom cover 270 may bein close contact to the lower surface of the substrate 210. The bottomcover 270 may be a protective film protecting the backlight unit 200.

Meanwhile, the display device may include a display module 20, indetail, a power supplier 400 that supplies driving voltage to thedisplay panel 100 and the backlight unit 200, and for example, the lightsources 220 of the backlight unit 200 can be driven to emit light by thevoltage supplied from the power supplier 400.

As shown in FIG. 12, the power supplier 400 may be fixed to a back cover40 covering the rear side of the display module 20 to be stablysupported and fixed.

According to an embodiment of the present invention, a first connector410 may be formed on the substrate 210, and for this configuration, ahole may be formed in the bottom cover 270 to insert the first connector410.

The first connector 410 electrically connects the light source 220 withthe power supplier 400 such that driving voltage is supplied from thepower supplier 400 to the light source 220.

For example, the first connector 410 may be disposed beneath thesubstrate 210 and connected with the power supplier 400 through a firstcable 420 to transmit driving voltage supplied from the power supplier400 through the first cable 420 to the light source 220.

An electrode pattern (not shown), for example, a carbon nanotubeelectrode pattern may be formed on the substrate 210. The electrodeformed on the substrate 210 can electrically connect the first connector410 with the light source 220, in contact with the electrode formed inthe light source 212.

Further, the display device may include a controller 500 controlling thedisplay panel 100 and the backlight unit 200, and for example, thecontroller 500 may be a timing controller.

The timing controller controls the driving timing of the display panel100, and in detail, creates signals for controlling the driving timingsof a data driving unit (not shown), a gamma voltage generating unit (notshown), and a gate driving unit (not shown) included in the displaypanel 100 and transmits the signals to the display panel 100.

Meanwhile, the timing controller can supply a signal for controlling thedriving timing of the light sources 220 to drive the backlight unit 200,in detail, the light sources 220, to the backlight unit 200, when thedisplay panel 100 is driven.

As shown in FIG. 12, the controller 500 may be fixed to a back cover 40covering the rear side of the display module 20 to be stably supportedand fixed.

According to an embodiment of the present invention, a second connector510 may be formed on the substrate 210, and for this configuration, ahole may be formed in the bottom cover 270 to insert the secondconnector 510.

The second connector 510 electrically connects the substrate 210 withthe controller 500 such that a control signal outputted from thecontroller 500 can be transmitted to the substrate 210.

For example, the second connector 510 may be disposed beneath thesubstrate 210 and connected with the controller 500 through a secondcable 520 to transmit a control signal supplied from the controller 500through the second cable 520 to the substrate 210.

Meanwhile, a light driving unit (not shown) may be formed on thesubstrate and can drive the light sources 220, using the control signalsupplied from the controller 500 through the second connector 510.

The configuration of the display device shown in FIG. 12 is providedjust as an embodiment and accordingly, if needed, it is possible tochange the position and the number of the power supplier 400, thecontroller 500, the first and second connectors 410 and 510, and thefirst and second cables 420 and 520.

For example, the first and second connectors 410 and 510 may be providedfor each of the optical assemblies 10 of the backlight unit, as shown inFIG. 11, and the power supplier 400 or the controller 500 may bedisposed beneath the bottom cover 270.

FIG. 13 is a block diagram showing the configuration of a display deviceaccording to a first embodiment of the present invention, in which thedisplay device may include a controller 600, a BLU driver 610, a paneldriver 620, a backlight unit 200, and a display panel 100. Further, inthe configuration of the display device shown in FIG. 13, the same partsas those described with reference to FIGS. 1 to 12 are not describedbelow.

Referring to FIG. 13, the display panel 100 can display an image at 60,120, or 240 frames per second, and the larger the number of frames persecond, the shorter the scan period T of the frames.

The panel driver 620 generates driving signals for driving the displaypanel in response to a variety of control signals and image signalsinputted from the controller 600, and transmits the driving signals tothe display panel 100. For example, the panel driver 620 may include agate driving unit connected with a gate line of the display panel 100, adata driving unit (not shown), and a timing controller (not shown)controlling those units.

Meanwhile, the controller 600 can output a local dimming value to theBLU driver 610 according to the image signal to control the backlightunit 200, in detail, the luminance of the light sources in the backlightunit 200 in response to the image signal.

Further, the controller 600 can supply information on the scan period Tdisplaying one frame on the display panel 100, for example, a verticalsynchronization signal Vsync to the driving unit 610.

The BLU driver 610 can control the light sources in the backlight unit200 to emit light in accordance with the scan period T insynchronization with display of an image on the display panel 100.

On the other hand, each of the light sources in the backlight unit 200may include a plurality of point light sources, for example, LEDs (LightEmitting Diodes), and the point light sources in one block can besimultaneously turned on or off.

Meanwhile, according to an embodiment of the present invention, thelight sources in the backlight unit 200 can be divided into a pluralityof blocks by the division driving method, such as local dimmingdescribed above, and the luminance of the light sources pertaining toeach block can be adjusted in accordance with the luminance of a regioncorresponding to each of the divided blocks in the display panel 100,for example, the gray level peak value or the color coordinate signal.

For example, when an image is displayed in a first region of the displaypanel 100 and an image is not displayed in a second region, that is, thesecond region is black, the BLU driver 610 can control the backlightunit 200, in detail, the light sources in the backlight unit 200 suchthat the light sources pertaining to the blocks corresponding to thesecond region in the divided blocks emit light at lower luminance thanthe light sources pertaining to the blocks corresponding to the firstregion.

Meanwhile, the light sources pertaining to the blocks of the backlightunit 200 which correspond to the second region that is black withoutdisplaying an image in the display image of the display panel 100 may beturned off, such that it is possible to reduce power consumed by thedisplay device.

That is, the controller 600 creates and outputs local dimming valuescorresponding to the brightness of the blocks of the backlight unit 200,that is, local dimming values for each block, in accordance with theluminance level of the input image signal, for example, the luminancelevel of the entire image or the luminance level at a predeterminedregion, and the BLU driver 610 can control the brightness of the blocksin the backlight unit 200, using the input local dimming values for eachblock.

A method of driving a display device according to an embodiment of thepresent invention is described hereafter in detail with reference toFIGS. 14 to 19.

FIG. 14 is a block diagram showing the configuration of a display deviceaccording to a second embodiment of the present invention, and theconfiguration of the display device shown in FIG. 14, the same parts asthose described with reference to FIGS. 1 to 13 are not described below.

Referring to FIG. 14, a display device according to an embodiment of thepresent invention an image analyzing unit 601 that determines theluminance level for the entire of a portion of an image in response toan RGB signal, a brightness determining unit 602 that determines thebrightness of a light source, for example an LED, which corresponds tothe luminance level determined by the image analyzing unit 601, and aBLU driver 610 that drives the backlight unit 200 in accordance with thebrightness level determined by the brightness determining unit 602.

Further, the display device may include a pixel compensator 603 thatchange the luminance level for the RGB image signal in consideration ofthe luminance level of an image analyzed by the image analyzing unit 601and a panel driver 620 that outputs an driving signal to the displaypanel 100 such that an image is outputted in response to the R′G′B′signal compensated by the pixel compensator 603.

The image analyzing unit 601 divides the region of the image intoseveral regions in response to the input RGB signal and suppliesinformation on the luminance level of an image to the brightnessdetermining unit 602 to determine the brightness of the light sourcespertaining to the blocks corresponding to the regions in the backlightunit 200.

For example, the information on the luminance level of the imagesupplied from the image analyzing unit 601 to the brightness determiningunit 602 may include not only the ABL (Average Block Level), averageluminance level of the region corresponding to a block to determine itsbrightness, but of another region adjacent to the above-mentioned regionor the APL (Average Picuture Level), average luminance level of theentire region of the image.

In other words, the image analyzing unit 601 can divide the image of oneframe into a plurality of regions and supply information on not only theaverage luminance level for a divided first region, but the averageluminance level for another region adjacent to the first region, to thebrightness determining unit 602. Further, when the brightnessdetermining unit 602 determines the brightness of a specific block inthe backlight unit 200, the image analyzing unit 601 can providecorresponding information to allow the brightness determining unit 602to use the average luminance level of the entire image.

According to an embodiment of the present invention, it is required toinclude a look-up table that determines the brightness of a specificblock in the backlight unit 200 in accordance with the average luminancelevel of the entire or a portion of the measured image, and thebrightness determining unit 602 can read out and output the brightnessof a light source corresponding to the average luminance level measuredby the image analyzing unit 601 from the look-up table.

FIG. 15 is a graph showing a first embodiment of a method of determiningthe brightness of a light source to the average luminance level of animage, in which the x-axis represents the ABL of a divided region of thedisplay panel 210, the y-axis represents the brightness of a blockcorresponding to the divided region in the backlight unit 100, and thez-axis represents the APL of the entire region.

Referring to FIG. 15, when the APL of the entire image is less than ‘A’,the brightness of a corresponding block of the backlight unit 200 isdetermined by a first graph 3A, when the APL of the entire image is ‘A’or more and less than ‘B’, the brightness of a corresponding block ofthe backlight unit 200 is determined by a second graph 3B, and when theAPL of the entire image is ‘B’ or more, the brightness of the block ofthe backlight unit 200 is determined by a third graph 3C.

For example, when the APL of the entire image is a predetermined ‘B’ ormore, since the entire image should be displayed bright, the brightnessof the corresponding block of the backlight unit 200 can be determinedby the third graph 3C. In this case, since the entire image to displayon the image panel 100 is bright, it does not matter that the imagedarkens with the local dimming effect of the backlight unit 200maximized.

In other words, when the entire image should be displayed bright, thelarger the average luminance level measured for each divided region ofthe image, the higher the brightness of corresponding blocks, whereasthe smaller the average luminance of the divided regions, the lower thebrightness of the corresponding blocks. For reference, the figure showsthat the graph representing the brightness of the LED to the averageluminance level at each divided region has one inclination.

On the other hand, when the entire image should be displayed dark, thatis, the APL of the entire image is less than ‘A’, the local dimming canbe applied only to the divided regions having average luminance levelsmaller than a predetermined luminance.

That is, the proposed look-up table makes it possible to apply the localdimming that changes the brightness of the light sources only for thedivided region having average luminance level smaller than thepredetermined luminance. This is because when the entire image is darkand the brightness of the light source is determined by the localdimming graph, such as the third graph 3C, the image becomes too darkand the color reproduction is deteriorated.

Therefore, when the luminance level of the entire image is low, thelocal dimming is not applied to the divided regions having averageluminance level above a predetermined brightness.

Further, when the APL of the entire image is in between ‘A’ and ‘B’ andthe average luminance level of a measured divided region is larger thana predetermined value, it is required to decrease changes in brightnessof the light source, and when the average luminance level of the dividedregion is smaller than the predetermined value, it is required toincrease changes in brightness of the light source. That is, it ispossible to set a small local dimming value corresponding to the lightsource in bright divided regions, and set a relatively large localdimming value corresponding to the light source in less bright dividedregions than the above divided regions.

The graph showing the brightness of a light source to average luminancelevels according to the look-up table is stored when the APL of theentire image is the maximum MAX and the APL of the entire image is theminimum MIN, and the table corresponding to the APL of the entire imageto measure may be determined between the maximum and minimum graphs ofthe APL of the entire image.

FIG. 16 shows by way of an example that a graph 4C that is applied whenthe APL of the entire image is the maximum MAX and a graph 4A that isapplied when the APL is the minimum MIN. That is, when the APL of theentire image is at the maximum, the brightness of the image is themaximum, and accordingly, even if the local dimming is applied to thedivided regions, the color reproduction is not deteriorated and a largeamount of power consumed by the backlight unit 200 can be reduced.

Further, when the APL of the entire image is at the minimum, thebrightness of the image is the minimum; therefore, in this case, thecolor reproduction of the image is deteriorated if the local dimming isapplied to the entire image. Accordingly, in this case, it is possibleto prevent the color reproduction from largely decreasing and reduce thepower consumed in driving the backlight unit, by applying the localdimming to the divided region corresponding to when the ABL of thedivided region is smaller than a predetermined value 4AA.

Further, when the APL of the entire image is not the maximum or theminimum, it is possible to create a desired look-up table (graph) byinterpolating the graphs 4A and 4C. That is, brightness determining unit602 can create a new graph positioned within a region defined by thegraphs 4A and 4C, using the look-up tables when the APL of the entireimage is the maximum and the minimum.

According to another embodiment of the present invention, the imagesignal transmitted to the display panel 100, for example, the RGB signalcan be compensated.

In other words, when the local dimming is applied to the backlight unit200 described above, there may be regions (or pixels) to display colorsin the divided regions of the display panel 100. In this case, it ispossible to reduce incomplete reproduction of colors due to the localdimming by adding a gain according to the luminance level of the entireimage to the RGB signal transmitted to the panel driver 620.

For example, when the local dimming is applied to a specific region inthe image, since the ABL of the corresponding divided region is low,there may be characters or images that should be displayed in thedivided region, even if the degree of the local dimming is large. Thatis, when the entire APL is low, high local dimming is applied and theentire image is displayed dark; therefore, even the characters or imagesto display may be displayed dark.

In this case, it is possible to implement color reproduction for thecharacters or images by improving the luminance level of the RGB signaltransmitted to the display panel 210 while maintaining the reductioneffect of the power consumed by the local dimming.

The pixel compensator 603 can compensate the image signal by multiplyingthe luminance level of the input RGB signal by a compensation value α,and for example, can estimate the compensation value α, using the APL ofthe entire image measured by the image analyzing unit 601.

FIG. 17 is a graph showing an embodiment of a method of determining acompensating value α of an image signal to the average luminance levelof an image.

Referring to FIG. 17, relatively large compensation can be performedwhen the image is dark, and the saturation frequency of the RGB valuecan be reduced by decreasing the compensation value α when the image isbright, such that more natural compensation can be performed to thepixel.

The x-axis represents the APL of the entire image measured by the imageanalyzing unit 601 and the y-axis represents a compensation value α forcompensating the pixel of the RGB signal corresponding thereto, in thegraph shown in FIG. 17.

That is, when the local dimming is not applied or the local dimmingvalue is a predetermined reference value, for example, 5A or less, thecompensation value α for compensating the pixel is set to 1, and as thelocal dimming value becomes closer to the maximum value MAX, thecompensation value α can be increased above 1. Therefore, the pixel canbe compensated as much as the darkening of the substantially shownimages of the characters or images by the local dimming.

Meanwhile, the compensated characters or images may imply regions wherethe gain of the RGB image signal is above a predetermined value.

According to another embodiment of the present invention, the controller600 may further include a filtering unit (not shown) correcting thebrightness level determined by the brightness determining unit 602, forexample, in order to the brightness of the LED from rapidly changingwith respect to time.

FIG. 18 is a view showing the configuration of a BLU driver included ina display device, in which, in the operation of the BLU 610, the sameparts as those described with reference to FIGS. 13 to 17 are notdescribed below.

Referring to FIG. 18, the BLU driver 610 is inputted from local dimmingvalues for each block representing the brightness of the divided blocksof the backlight unit 200 from the controller 600, in detail, thebrightness determining unit 602 of the controller 600, and can output aplurality of driving signals, for example first to m-th driving signals,using the input local dimming values for each block.

Meanwhile, each of the driving signals outputted from the BLU driver 610can control the brightness of two or more blocks of the divided blocksin the backlight unit 200.

In other words, the BLU driver 610 can create a first driving signal forcontrolling the brightness of n blocks, for example, the first to n-thblocks in the blocks of the backlight unit 200 and supply the firstdriving signal to the light sources pertaining to the first to n-thblocks, and for this configuration, it is possible to create the firstdriving signal, using the local dimming values corresponding to thefirst to n-th blocks in the local dimming values for each block inputtedfrom the controller 600.

According to an embodiment of the present invention, the controller 600and the BLU driver 610 can communicate signals with each other, usingSPI (Serial Peripheral Interface) communication, that is, the BLU driver610 can receive local dimming values for each block from the controller600, using the SPI communication.

Referring to FIG. 19, the BLU driver 610 may include a plurality ofdriving units 611 and 615, and the driving units 611 and 615 may includeMCUs 612 and 616 and a plurality of drivers IC 613 and 617,respectively.

For example, the first driving unit 611 includes an MCU 612 and aplurality of driver ICs 613, and the MCU 612 can receive in series localdimming values for each block from the controller 600, in detail thebrightness determining unit 602 of the controller 600, and then outputthem in parallel and transmit local dimming values of correspondingblocks to the driver ICs 613.

Meanwhile, the driver ICs 613 can control the brightness of n blocks ofthe divided block in the backlight unit 200, and for this configuration,it is possible to output driving signals for controlling the brightnessof the n blocks, using n channels.

For example, the first driving unit 611 may include four driver ICs 613and each of the four driver ICs 613 can control the brightness of thelight sources pertaining to sixty blocks by outputting driving signals,using sixty channels. Accordingly, the first driving unit 611 cancontrol the brightness of 4×16 blocks, i.e. sixty four blocks in thedivided blocks of the backlight unit 200.

For example, the second driving unit 615 includes an MCU 616 and aplurality of driver ICs 613, and the MCU 616 can receive in series localdimming values for each block from the controller 600, in detail thebrightness determining unit 602 of the controller 600, and then outputthem in parallel and transmit local dimming values of correspondingblocks to the driver ICs 617.

Meanwhile, the driver ICs 617 can control the brightness of n blocks ofthe divided block in the backlight unit 200, and for this configuration,it is possible to output driving signals for controlling the brightnessof the n blocks, using n channels.

The configuration of the BLU driver 610 shown in FIG. 19 is nothing butan embodiment of the present invention; therefore, a display deviceaccording to the present invention is not limited to the configurationshown in FIG. 19. That is, the BLU driver 610 may include three or moredriving units, and the number of blocks of the backlight unit 200 ofwhich the brightness is controlled by the driving units can be changed.

Although the present invention was described in the above with referenceto the preferred embodiments, the embodiment are provided just asexamples and do not limit the present invention. Further, the presentinvention may be modified and applied in various ways not exemplified inthe above within the spirit and scope of the present invention by thoseskilled in the art. For example, the components described in detail inthe embodiments of the present invention may be modified. Further,differences in the modification and application should be construed asbeing included in the scope of the present invention, which is definedin the accompanying claims.

1. A display device comprising: a backlight unit that is divided into aplurality of blocks and is driven by the divided blocks, and includes atleast one optical assembly; a display panel positioned over thebacklight unit; a controller that outputs local dimming valuescorresponding to brightness of the blocks of the backlight unit, inaccordance with an image displayed in the display panel; and a BLUdriver that controls brightness of the blocks of the backlight unitusing the local dimming values, wherein the optical assembly includes: afirst layer; a plurality of light sources that are formed on the firstlayer and emit light, and a light emitting surface of the light sourcebeing formed in the direction crossing the first layer, and at least twoof the light sources emitting lights in different directions from eachother; a second layer disposed above the first layer to cover the lightsources; and a reflective layer that is disposed between the first andsecond layers, wherein the BLU driver receives the local dimming valuesand outputs a plurality of driving signals, and the driving signalscontrol the brightness of two or more blocks among the blocks of thebacklight unit respectively.
 2. The display device according to claim 1,wherein the display panel is divided into a plurality of regions and thecontroller adjusts the brightness of the blocks in the backlight unitwhich correspond to the regions, in accordance with luminance of theregions of the display panel.
 3. The display device according to claim2, wherein the controller includes: an image analyzing unit thatmeasures the average picture level of an image; and a brightnessdetermining unit that determines the local dimming values for each blockof the backlight unit, using the measured average picture level of theimage.
 4. The display device according to claim 3, wherein thebrightness determining unit determines the brightness of a light sourceincluded in the blocks of the backlight unit which correspond to a firstregion, using the average picture level of the image and the averagepicture level of the first region in the display panel.
 5. The displaydevice according to claim 3, further comprising: a pixel compensatorthat adjust a luminance level of an input image signal, using themeasured average picture level of the image; and a panel driver thatdrives the display panel in response to the image signal outputted fromthe pixel compensator.
 6. The display device according to claim 1,wherein the BLU driver receives the local dimming values for each blockfrom the controller, using SPI (Serial Peripheral Interface)communication.
 7. The display device according to claim 1, wherein thefirst layer is a substrate with the light sources mounted thereon. 8.The display device according to claim 1, wherein the second layerincludes silicon-based or acryl-based resin.
 9. The display deviceaccording to claim 1, wherein the second layer includes a plurality ofdispersed particles.
 10. The display device according to claim 1,further comprising: light-shielding patterns that are formed on thesecond layer to correspond to the positions of the light sources. 11.The display device according to claim 1, wherein the backlight unitincludes a plurality of the optical assemblies.
 12. The display deviceaccording to claim 1, wherein the second layer is 0.1 to 4.5 mm thick.13. The display device according to claim 1, wherein the light sourcesincluded in the optical assembly are driven in two or more dividedblocks.
 14. A display device, comprising: a backlight unit that isdivided into a plurality of blocks and is driven by the divided blocks,and includes at least one optical assembly; a display panel positionedover the backlight unit; a first controller that outputs local dimmingvalues corresponding to brightness of the blocks of the backlight unit,in accordance with an image displayed in the display panel; and a BLUdriver that controls brightness of the blocks of the backlight unitusing the local dimming values, wherein the optical assembly includes: afirst layer; a plurality of light sources that is are formed on thefirst layer and emit light, and a light emitting surface of the lightsource being formed in the direction crossing the first layer, and atleast two of the light sources emitting lights in different directionsfrom each other; a second layer disposed above the first layer to coverthe light sources; and a reflective layer that is disposed between thefirst and second layers, and wherein the BLU driver includes a drivingunit, and the driving unit includes a second controller that receiveslocal dimming values from the first controller and a plurality of driverICs that output driving signals for controlling the brightness of thetwo or more blocks respectively.
 15. The display device according toclaim 14, wherein the second controller outputs the local dimming valuesinputted in parallel, and then transmits the local dimming values foreach block to the driver ICs.
 16. The display device according to claim14, wherein the driver ICs transmit driving signal to the light sourcesincluded in n blocks, using n channels, and n represents a number. 17.The display device according to claim 14, wherein the BLU driverincludes a plurality of the driving units.
 18. The display deviceaccording to claim 14, wherein the light sources included in the opticalassembly are driven in two or more divided blocks.
 19. The displaydevice according to claim 14, wherein the backlight unit includes aplurality of the optical assemblies.
 20. The display device according toclaim 1, wherein the plurality of light sources are disposed as a firstlight source array and a second light source array, the first lightsource array includes first lines of light sources among the pluralityof light sources, the second light source array includes second lines oflight sources among the plurality of light sources, and the first andsecond lines are alternatively disposed.
 21. The display deviceaccording to claim 20, wherein the light sources included in the firstlight source array and the light sources included in the second lightsource array emit light in different directions from each other.
 22. Thedisplay device according to claim 20, wherein a light emitting surfaceof a first light source included in the first light source array faces afirst direction, and a light emitting surface of a second light sourceincluded in the second light source array faces a second directiondifferent form the first direction.
 23. The display device according toclaim 10, wherein at least one of the light-shielding patterns has areflectance that decreases outwardly from a portion of the at least oneof the patterns corresponding to a center portion of the correspondinglight source.
 24. The display device according to claim 10, wherein acenter of at least one of the light-shielding patterns is disposed apredetermined distance from a center of the corresponding light sourcein a first direction.
 25. The display device according to claim 1,further comprising: at least one reflection layer between the firstlayer and the second layer, and wherein the reflection layer includes atleast a first portion and a second portion having differentreflectances.
 26. The display device according to claim 25, furthercomprising: a plurality of patterns formed on the reflection layer,wherein the reflection layer includes an area in which a density of thepatterns increases.